Spatio-temporal Evolution Of Hydro-Meteorological Processes In The Upper Reaches Of The Yangtze River And Future Scenario Estimates

Analysing the spatial and temporal variation of water resources in a basin is helpful for us to understand the distribution and evolution characteristics of water resources,which can provide important theoretical basis for water resources management and hydropower energy optimization dispatch of the basin.However,only using historical measured hydro-meteorological data to do the research of spatio-temporal variation of water resources in the Yangtze River Basin isn't enough to meet the actual status of the project.It's necessary to integrate multi-source hydro-meteorological data together with appropriate methods to analyze and predict climate change.Therefore,surrounded by the evolution of the hydro-meteorological processes of the upper reaches of the Yangtze River,based on measured hydro-meteorological factors,this paper integrates reanalysis precipitation data and three global climates,GFDL-ESM2M,IPSL-CM5A-LR and NOR-ESM-M of CMIP5 to analyze the spatio-temporal patterns of the hydro-meteorological processes of the field and to predict the spatio-temporal patterns of hydro-meteorological processes under different climate change scenarios.The main contents and research results of the paper are as follows:(1)Using the measured precipitation to evaluate the applicability of the ERA-interim reanalysis precipitation data in the field,the results show that the value of the ERA data are larger than of measured precipitation,but the consistency of the trend of the precipitation series at different time scales is high.Correcting the ERA precipitation data by the conversion coefficient,the obtained ERA fitting sequence has a good fitting effect with the measured values.In addition,in order to analyze the applicability of the precipitation data of the three global climate model in CMIP5,the revised ERA precipitation sequence and the annual SPI indices of the measured values were used to evaluate the historical precipitation of the three global climate models.The results show that the interannual precipitation in the historical period of the three models is close to the measured change,and the annual and seasonal precipitation passing rates within 20%of the precipitation deviation is above 70%.The average multi-year precipitation also conforms to the actual situation.Therefore,the three precipitation models simulated by the global climate model can reflect the actual situation of the basin to a certain extent,and the precipitation data has a good applicability in the field.(2)Spatio-temporal evolution of water resources in the basin was analyzed with annual,seasonal,maximum daily precipitation,heavy precipitation,and standardized precipitation indices of the measured.It shows that the precipitation series showed a steady change from 1970 to 2012,and the annual precipitation trend rate showed the largest change.The rate in the spatial of annual and seasonal precipitation in the field show an increasing trend from southeast to northwest.The largest daily precipitation in the source of the basin showed a slight upward trend,mainly concentrated in the central-southwest-eastern extension of the field.The heavy rainfall increased slightly,mainly in the west and east of the basin.For meteorological drought indicators,the longer the time scale,the more years of floods and droughts occur in the basin.The drought year is larger than the flood years and the time scale increases,the special drought year also increases.On the spatial scale,for longer time scale,the area of floods decreased,and the range of drought regions increased.(3)Further forecasting the precipitation and climatic droughts and floods in the field,the estimated precipitation data of the three global climate models were used to analyze the evolution characteristics of the two time periods in regions of 2006-2035 and 2036-2065.It shows that years from 2006 to 2035,annual and summer precipitation have large amplitudes,and the annual precipitation rate of the IPSL model in RCP2.6 scenario is 35mm/(10a),and the characteristics of the maximum daily precipitation and heavy precipitation are not obvious.Spatially,the patterns in different scenarios are different,but the overall change is small.The drought and flood seasons of SPI in different time scales were concentrated in the middle and late periods,but droughts and floods changed frequently during the whole period.The probability of occurrence of disaster years was close to 1/3,of which,the dry and wet changes of the basin were most significant under the IPSL mode RCP2.6 scenario.On the spatial scale,as the time scale increases,the degree of wetting in the basin increases.From 2036 to 2065,annual and summer precipitation did not change significantly during the previous period.The overall change in extreme precipitation indicators is small.For meteorological drought indicators,the larger the time scale,the greater the proportion of disasters,the longer the duration,and the greater the probability of disasters in the early and late 2036-2065 years.In terms of spatial changes,for longer time scale,the proportion of watershed aridity also increases,concentrating on the southeastern part of the basin.